Fuel cell module

ABSTRACT

A fuel cell module includes a first area where an exhaust gas combustor and a start-up combustor are provided, an annular second area disposed around the first area where a heat exchanger is provided, an annular third area disposed around the second area where a reformer is provided, and an annular fourth area disposed around the third area where an evaporator is provided. The fuel cell module includes a first partition plate having first combustion gas holes, a second partition plate having second combustion gas holes, and a third partition plate having third combustion gas holes.

TECHNICAL FIELD

The present invention relates to a fuel cell module including a fuelcell stack formed by stacking a plurality of fuel cells for generatingelectricity by electrochemical reactions between a fuel gas and anoxygen-containing gas.

BACKGROUND ART

Typically, a solid oxide fuel cell (SOFC) employs a solid electrolytemade of an ion-conductive oxide such as stabilized zirconia. Theelectrolyte is interposed between an anode and a cathode to form anelectrolyte electrode assembly (hereinafter also referred to as an MEA).The electrolyte electrode assembly is interposed between separators.During use thereof, generally, a predetermined number of the electrolyteelectrode assemblies and the separators are stacked together to form afuel cell stack.

As a system including this type of fuel cell stack, for example, thefuel cell battery disclosed in Japanese Laid-Open Patent Publication No.2001-236980 (hereinafter referred to as conventional technique 1) isknown. As shown in FIG. 13, the fuel cell battery includes a fuel cellstack 1 a, and a heat insulating sleeve 2 a provided at one end of thefuel cell stack 1 a. A reaction device 4 a is provided in the heatinsulating sleeve 2 a. The reaction device 4 a includes a heat exchanger3 a.

In the reaction device 4 a, as a treatment for a liquid fuel, partialoxidation reforming, which does not use water, is performed. After theliquid fuel is evaporated by an exhaust gas, the liquid fuel passesthrough a feeding point 5 a, which forms part of the heat exchanger 3 a.The fuel contacts an oxygen carrier gas heated by the exhaust gas toinduce partial oxidation reforming, and thereafter, the fuel is suppliedto the fuel cell stack 1 a.

Further, as shown in FIG. 14, the solid oxide fuel cell disclosed inJapanese Laid-Open Patent Publication No. 2010-504607 (PCT) (hereinafterreferred to as conventional technique 2) has a heat exchanger 2 bincluding a cell core 1 b. The heat exchanger 2 b heats air at thecathode utilizing waste heat.

Further, as shown in FIG. 15, the fuel cell system disclosed in JapaneseLaid-Open Patent Publication No. 2004-288434 (hereinafter referred to asconventional technique 3) includes a first area is having a verticallyextending columnar shape, and an annular second area 2 c disposed aroundthe first area 1 c, an annular third area 3 c disposed around the secondarea 2 c, and an annular fourth area 4 c disposed around the third area3 c.

A burner 5 c is provided in the first area 1 c, and a reforming pipe 6 cis provided in the second area 2 c. A water evaporator 7 c is providedin the third area 3 c, and a CO shift converter 8 c is provided in thefourth area 4 c.

SUMMARY OF INVENTION

In conventional technique 1, at the time of performing partial oxidationreforming in the reaction device 4 a, heat from the exhaust gas is usedfor heating the liquid fuel and the oxygen carrier gas. Therefore, thequantity of heat required for heating the oxygen-containing gas suppliedto the fuel cell stack 1 a tends to be insufficient. Thus, a thermallyself-sustaining operation cannot be performed effectively.

Further, in conventional technique 2, exhaust heat is used for heatingthe cathode air supplied to the cell core 1 b. Therefore, the heatquantity required for reforming or heating of the fuel gas supplied tothe cell core 1 b tends to be insufficient. Thus, together withreforming, a thermally self-sustaining operation cannot be performedsuitably.

Further, in conventional technique 3, heat from the combustion gas fromthe burner 5 c is used for reforming the fuel. Therefore, theoxygen-containing gas supplied to the fuel cell may not be heatedsufficiently, and thus, a thermally self-sustaining operation cannot beperformed effectively.

The present invention has been made to solve the aforementioned problemsof this type, and has the object of providing a fuel cell module havinga simple and compact structure, which makes it possible to improve heatefficiency and to facilitate a thermally self-sustaining operation.

The present invention relates to a fuel cell module comprising a fuelcell stack formed by stacking fuel cells for generating electricity byelectrochemical reactions between a fuel gas and an oxygen-containinggas, a reformer for reforming a mixed gas of water vapor and a raw fuelchiefly containing hydrocarbon to produce the fuel gas supplied to thefuel cell stack, an evaporator for evaporating water, and supplying thewater vapor to the reformer, a heat exchanger for raising temperature ofthe oxygen-containing gas by heat exchange with combustion gas, andsupplying the oxygen-containing gas to the fuel cell stack, an exhaustgas combustor for combusting the fuel gas discharged from the fuel cellstack as a fuel exhaust gas and the oxygen-containing gas dischargedfrom the fuel cell stack as an oxygen-containing exhaust gas to therebyproduce the combustion gas, and a start-up combustor for combusting theraw fuel and the oxygen-containing gas to thereby produce the combustiongas.

The fuel cell module further comprises a first area where the exhaustgas combustor and the start-up combustor are provided, an annular secondarea disposed around the first area where one of the reformer and theheat exchanger is provided, an annular third area disposed around thesecond area where another of the reformer and the heat exchanger isprovided, an annular fourth area disposed around the third area wherethe evaporator is provided, a first partition plate provided between thefirst area and the second area, a second partition plate providedbetween the second area and the third area, and a third partition plateprovided between the third area and the fourth area.

First combustion gas holes, second combustion gas holes, and thirdcombustion gas holes are formed in the first partition plate, the secondpartition plate, and the third partition plate, respectively, forthereby allowing the combustion gas to flow through the first area, thesecond area, the third area, and the fourth area.

In the present invention, the annular second area is disposed at thecenter around the first area where the exhaust gas combustor and thestart-up combustor are provided, the annular third area is disposedaround the second area, and the annular fourth area is disposed aroundthe third area. In such a structure, hot temperature equipment with alarge heat demand can be provided on the inside, and low temperatureequipment with a small heat demand can be provided on the outside.Accordingly, an improvement in heat efficiency is achieved, and athermally self-sustaining operation is facilitated. Further, a simpleand compact structure is achieved.

The first partition plate, the second partition plate, and the thirdpartition plate separate the first area, the second area, the thirdarea, and the fourth area from each other. Further, the first combustiongas holes, the second combustion gas holes, and the third combustion gasholes are formed in the first partition plate, the second partitionplate, and the third partition plate, respectively, for allowing thecombustion gas to flow through the first area, the second area, thethird area, and the fourth area.

In such a structure, blowing of the combustion gas can be suppressedsuitably, a further improvement in heat efficiency is achieved, and athermally self-sustaining operation can be facilitated reliably.

Further, positions of the first combustion gas holes, the secondcombustion gas holes, and the third combustion gas holes can bedetermined depending on a priority of any one of heat exchangeefficiency, durability, and a reduction in size or the like with respectto the second, third, and fourth areas. Accordingly, the target heatexchange efficiency can be determined freely, and a wider variety ofdesigns becomes available.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically showing the structure of a fuel cellsystem including a fuel cell module according to a first embodiment ofthe present invention;

FIG. 2 is a perspective view with partial omission showing FC peripheralequipment of the fuel cell module;

FIG. 3 is an exploded perspective view showing main components of the FCperipheral equipment;

FIG. 4 is an enlarged perspective view showing main components of the FCperipheral equipment;

FIG. 5 is a view showing gas flows of a combustion gas in the FCperipheral equipment;

FIG. 6 is a graph showing the temperature at a heat transmission surfacewhere gases flow in a counterflowing manner;

FIG. 7 is a graph showing the temperature at a heat transmission surfacewhere gases flow in parallel with each other;

FIG. 8 is a view showing combustion gas holes;

FIG. 9 is a diagram schematically showing the structure of a fuel cellsystem including a fuel cell module according to a second embodiment ofthe present invention;

FIG. 10 is a perspective view with partial omission showing FCperipheral equipment of the fuel cell module;

FIG. 11 is a view showing gas flows of a combustion gas in the FCperipheral equipment;

FIG. 12 is a view showing gas extraction holes;

FIG. 13 is a view schematically showing the fuel cell battery disclosedin conventional technique 1;

FIG. 14 is a partially cutaway perspective view, showing the solid oxidefuel cell disclosed in conventional technique 2; and

FIG. 15 is a view schematically showing the fuel cell system disclosedin conventional technique 3.

DESCRIPTION OF EMBODIMENTS

As shown in FIG. 1, a fuel cell system 10 includes a fuel cell module 12according to a first embodiment of the present invention. The fuel cellsystem 10 is used in various applications, including stationary andmobile applications. For example, the fuel cell system 10 may be mountedon a vehicle.

The fuel cell system 10 includes the fuel cell module (SOFC module) 12for generating electrical energy used for power generation byelectrochemical reactions between a fuel gas (a gas produced by mixinghydrogen gas, methane, and carbon monoxide) and an oxygen-containing gas(air), a raw fuel supply apparatus (including a fuel gas pump) 14 forsupplying a raw fuel (e.g., city gas) to the fuel cell module 12, anoxygen-containing gas supply apparatus (including an air pump) 16 forsupplying the oxygen-containing gas to the fuel cell module 12, a watersupply apparatus (including a water pump) 18 for supplying water to thefuel cell module 12, and a control device 20 for controlling the amountof electrical energy generated in the fuel cell module 12.

The fuel cell module 12 includes a fuel cell stack 24 formed by stackinga plurality of solid oxide fuel cells 22 in a vertical direction (or ahorizontal direction). The fuel cell 22 includes an electrolyteelectrode assembly (MEA) 32. The electrolyte electrode assembly 32includes a cathode 28, an anode 30, and an electrolyte 26 interposedbetween the cathode 28 and the anode 30. For example, the electrolyte 26is made of an ion-conductive oxide such as stabilized zirconia.

A cathode side separator 34 and an anode side separator 36 are providedon both sides of the electrolyte electrode assembly 32. Anoxygen-containing gas flow field 38 for supplying the oxygen-containinggas to the cathode 28 is formed in the cathode side separator 34, and afuel gas flow field 40 for supplying the fuel gas to the anode 30 isformed in the anode side separator 36. Various types of conventionalSOFCs can be adopted as the fuel cell 22.

The operating temperature of the fuel cell 22 is high, on the order ofseveral hundred ° C. Methane in the fuel gas is reformed at the anode 30to obtain hydrogen and CO, and hydrogen and CO are supplied to a portionof the electrolyte 26 adjacent to the anode 30.

An oxygen-containing gas supply passage 42 a, an oxygen-containing gasdischarge passage 42 b, a fuel gas supply passage 44 a, and a fuel gasdischarge passage 44 b extend through the fuel cell stack 24. Theoxygen-containing gas supply passage 42 a is connected to an inlet ofeach oxygen-containing gas flow field 38, the oxygen-containing gasdischarge passage 42 b is connected to an outlet of eachoxygen-containing gas flow field 38, the fuel gas supply passage 44 a isconnected to an inlet of each fuel gas flow field 40, and the fuel gasdischarge passage 44 b is connected to an outlet of each fuel gas flowfield 40.

The fuel cell module 12 includes a reformer 46 for reforming a mixed gasof water vapor and raw fuel which chiefly contains hydrocarbon (e.g.,city gas) to thereby produce a fuel gas that is supplied to the fuelcell stack 24, an evaporator 48 for evaporating water and supplyingwater vapor to the reformer 46, a heat exchanger 50 for raising thetemperature of the oxygen-containing gas through heat exchange with acombustion gas, and supplying the oxygen-containing gas to the fuel cellstack 24, an exhaust gas combustor 52 for combusting the fuel gas, whichis discharged as a fuel exhaust gas from the fuel cell stack 24, and theoxygen-containing gas, which is discharged as an oxygen-containingexhaust gas from the fuel cell stack 24, to thereby produce thecombustion gas, and a start-up combustor 54 for combusting the raw fueland the oxygen-containing gas to thereby produce the combustion gas.

Basically, the fuel cell module 12 is made up of the fuel cell stack 24and FC (fuel cell) peripheral equipment 56. FC peripheral equipment 56includes the reformer 46, the evaporator 48, the heat exchanger 50, theexhaust gas combustor 52, and the start-up combustor 54.

As shown in FIG. 2, the FC peripheral equipment 56 includes a first areaR1 comprising, e.g., a circular opening where the exhaust gas combustor52 and the start-up combustor 54 are provided, an annular second area R2formed around the first area R1 where the heat exchanger 50 is provided,an annular third area R3 formed around the second area R2 where thereformer 46 is provided, and an annular fourth area R4 formed around thethird area R3 where the evaporator 48 is provided.

As shown in FIGS. 2 and 3, the start-up combustor 54 includes an airsupply pipe 57 and a raw fuel supply pipe 58. The start-up combustor 54includes an ejector function for generating a negative pressure forsucking raw fuel in the raw fuel supply pipe 58 by flow of air suppliedfrom the air supply pipe 57.

As shown in FIGS. 2 and 4, the FC peripheral equipment 56 includes afirst partition plate 60 a provided between the first area R1 and thesecond area R2, a second partition plate 60 b provided between thesecond area R2 and the third area R3, and a third partition plate 60 cprovided between the third area R3 and the fourth area R4. Also, afourth partition plate 60 d is disposed around the fourth area R4 as anouter plate.

As shown in FIGS. 2 and 3, the exhaust gas combustor 52 is providedinside the first partition plate 60 a that contains the start-upcombustor 54. The first partition plate 60 a has a cylindrical shape. Aplurality of first combustion gas holes 62 a are formed along an outercircumferential portion of the first partition plate 60 a, adjacent toan end of the first partition plate 60 a close to the fuel cell stack24.

A plurality of second combustion gas holes 62 b are formed adjacent toan end of the second partition plate 60 b opposite from the fuel cellstack 24. A plurality of third combustion gas holes 62 c are formedadjacent to an end of the third partition plate 60 c close to the fuelcell stack 24. A plurality of fourth combustion gas holes 62 d areformed adjacent to an end of the fourth partition plate 60 d oppositefrom the fuel cell stack 24. The combustion gas is discharged to theexterior through the fourth combustion gas holes 62 d.

One end of an oxygen-containing exhaust gas channel 63 a and one end ofan fuel exhaust gas channel 63 b are provided respectively on the firstpartition plate 60 a. Combustion gas is produced inside the firstpartition plate 60 a by a combustion reaction between the fuel gas (morespecifically, a fuel exhaust gas) and the oxygen-containing gas (morespecifically, an oxygen-containing exhaust gas).

As shown in FIG. 1, the other end of the oxygen-containing exhaust gaschannel 63 a is connected to the oxygen-containing gas discharge passage42 b of the fuel cell stack 24, and the other end of the fuel exhaustgas channel 63 b is connected to the fuel gas discharge passage 44 b ofthe fuel cell stack 24.

As shown in FIGS. 2 and 3, the heat exchanger 50 includes a plurality ofheat exchange pipes (heat transmission pipes) 64 disposed around thefirst partition plate 60 a. The heat exchange pipes 64 are fixed to afirst inner ring 66 a at one end (i.e., the other end opposite from thefuel cell stack 24; hereinafter, in the same manner, the other endopposite from the fuel cell stack 24 is referred to as “one end”). Theheat exchange pipes 64 are fixed to a first inner ring 66 b at the otherend (i.e., one end closer to the fuel cell stack 24; hereinafter, in thesame manner, the one end closer to the fuel cell stack 24 is referred toas an “other end”).

A first outer ring 68 a is provided on the outside of the first innerring 66 a, and a first outer ring 68 b is provided on the outside of thefirst inner ring 66 b. The first inner rings 66 a, 66 b and the firstouter rings 68 a, 68 b are fixed respectively to the outercircumferential surface of the first partition plate 60 a, and to theinner circumferential surface of the second partition plate 60 b.

An annular oxygen-containing gas supply chamber 70 a is formed betweenthe first inner ring 66 a and the first outer ring 68 a, andoxygen-containing gas is supplied to the oxygen-containing gas supplychamber 70 a. An annular oxygen-containing gas discharge chamber 70 b isformed between the first inner ring 66 b and the first outer ring 68 b,and heated oxygen-containing gas is discharged into theoxygen-containing gas discharge chamber 70 b (see FIGS. 2 to 4).Opposite ends of each of the heat exchange pipes 64 open respectivelyinto the oxygen-containing gas supply chamber 70 a and theoxygen-containing gas discharge chamber 70 b.

An oxygen-containing gas supply pipe 72 is connected to theoxygen-containing gas supply chamber 70 a. One end of anoxygen-containing gas channel 74 is connected to the oxygen-containinggas discharge chamber 70 b, whereas the other end of theoxygen-containing gas channel 74 is connected to the oxygen-containinggas supply passage 42 a of the fuel cell stack 24 (see FIG. 1).

The reformer 46 is a preliminary reformer for reforming higherhydrocarbon (C₂₊) such as ethane (C₂H₆), propane (C₃H₈), and butane(C₄H₁₀) in the city gas (raw fuel), to thereby produce by steamreforming a fuel gas chiefly containing methane (CH₄), hydrogen, and CO.The operating temperature of the reformer 46 is several hundred ° C.

As shown in FIGS. 2 and 3, the reformer 46 includes a plurality ofreforming pipes (heat transmission pipes) 76 disposed around the heatexchanger 50. The reforming pipes 76 are fixed to a second inner ring 78a at one end thereof, and are fixed to a second inner ring 78 b at theother end thereof.

A second outer ring 80 a is provided outside of the second inner ring 78a, and a second outer ring 80 b is provided outside of the second innerring 78 b. The second inner rings 78 a, 78 b and the second outer rings80 a, 80 b are fixed respectively to the outer circumferential surfaceof the second partition plate 60 b, and to the inner circumferentialsurface of the third partition plate 60 c.

An annular mixed gas supply chamber 82 a is formed between the secondinner ring 78 a and the second outer ring 80 a. A mixed gas of raw fueland water vapor is supplied to the mixed gas supply chamber 82 a. Anannular reformed gas discharge chamber 82 b is formed between the secondinner ring 78 b and the second outer ring 80 b. The produced fuel gas(reformed gas) is discharged to the reformed gas discharge chamber 82 b.

Opposite ends of each of the reforming pipes 76 open respectively intothe mixed gas supply chamber 82 a and the reformed gas discharge chamber82 b. Reforming catalyst pellets 84 fill inside of each of the reformingpipes 76. Metal meshes 86 are disposed on opposite ends of the reformingpipes 76 for supporting and maintaining the catalyst pellets 84 insidethe reforming pipes 76.

A raw fuel supply channel 88 is connected to the mixed gas supplychamber 82 a, and a later-described evaporation return pipe 102 isconnected to a middle position of the raw fuel supply channel 88. Oneend of a fuel gas channel 90 is connected to the reformed gas dischargechamber 82 b, whereas the other end of the fuel gas channel 90 isconnected to the fuel gas supply passage 44 a of the fuel cell stack 24(see FIG. 1).

The evaporator 48 includes evaporation pipes (heat transmission pipes)92 disposed outside of and around the reformer 46. The evaporation pipes92 are fixed to a third inner ring 94 a at one end thereof, and arefixed to a third inner ring 94 b at the other end thereof.

A third outer ring 96 a is provided outside of the third inner ring 94a, and a third outer ring 96 b is provided outside of the third innerring 94 b. The third inner rings 94 a, 94 b and the third outer rings 96a, 96 b are fixed to the outer circumferential surface of the thirdpartition plate 60 c, and to the inner circumferential surface of thefourth partition plate 60 d.

An annular water supply chamber 98 a is formed between the third innerring 94 a and the third outer ring 96 a. Water is supplied to the watersupply chamber 98 a. An annular water vapor discharge chamber 98 b isformed between the third inner ring 94 b and the third outer ring 96 b.Water vapor is discharged to the water vapor discharge chamber 98 b.Opposite ends of the evaporation pipes 92 open into the water supplychamber 98 a and the water vapor discharge chamber 98 b, respectively.

A water channel 100 is connected to the water supply chamber 98 a. Oneend of the evaporation return pipe 102, which includes at least oneevaporation pipe 92, is provided in the water vapor discharge chamber 98b, whereas the other end of the evaporation return pipe 102 is connectedto a middle position of the raw fuel supply channel 88 (see FIG. 1). Theraw fuel supply channel 88 has an ejector function for generating anegative pressure as a result of the raw fuel flowing therein, forthereby sucking the water vapor.

As shown in FIG. 1, the raw fuel supply apparatus 14 includes a raw fuelchannel 104. The raw fuel channel 104 branches through a raw fuelregulator valve 106 into the raw fuel supply channel 88 and the raw fuelsupply pipe 58. A desulfurizer 108 for removing sulfur compounds in thecity gas (raw fuel) is provided in the raw fuel supply channel 88.

The oxygen-containing gas supply apparatus 16 includes anoxygen-containing gas channel 110. The oxygen-containing gas channel 110branches through an oxygen-containing gas regulator valve 112 into theoxygen-containing gas supply pipe 72 and the air supply pipe 57. Thewater supply apparatus 18 is connected to the evaporator 48 through thewater channel 100.

In the first embodiment, as schematically shown in FIG. 5, a firstcombustion gas channel 116 a, which serves as a passage for thecombustion gas, is formed in the first area R1, a second combustion gaschannel 116 b, which serves as a passage for the combustion gas in thedirection of the arrow A1, is formed in the second area R2, a thirdcombustion gas channel 116 c, which serves as a passage for thecombustion gas in the direction of the arrow A2, is formed in the thirdarea R3, and a fourth combustion gas channel 116 d, which serves as apassage for the combustion gas in the direction of the arrow A1, isformed in the fourth area R4.

Next, operations of the fuel cell system 10 will be described below.

At the time of starting operation of the fuel cell system 10, air(oxygen-containing gas) and raw fuel are supplied to the start-upcombustor 54. Specifically, air is supplied to the oxygen-containing gaschannel 110 by the operation of the air pump of the oxygen-containinggas supply apparatus 16. More specifically, air is supplied to the airsupply pipe 57 by adjusting the opening angle of the oxygen-containinggas regulator valve 112.

In the meantime, in the raw fuel supply apparatus 14, by operation ofthe fuel gas pump, for example, raw fuel such as city gas (containingCH₄, C₂H₆, C₃H₈, and C₄H₁₀) is supplied to the raw fuel channel 104. Rawfuel is supplied into the raw fuel supply pipe 58 by regulating theopening angle of the raw fuel regulator valve 106. The raw fuel is mixedwith air, and is supplied into the start-up combustor 54 (see FIG. 2).

Thus, mixed gas of raw fuel and air is supplied into the start-upcombustor 54, and the mixed gas is ignited to start combustion.Therefore, in the exhaust gas combustor 52, which is connected directlyto the start-up combustor 54, the combustion gas from the start-upcombustor 54 flows into the first partition plate 60 a.

As shown in FIG. 5, the plurality of first combustion gas holes 62 a areformed at the end of the first partition plate 60 a close to the fuelcell stack 24. Thus, combustion gas supplied into the first partitionplate 60 a passes through the first combustion gas holes 62 a, whereuponthe combustion gas flows from the first area R1 into the second area R2.

In the second area R2, the combustion gas flows in the direction of thearrow A1, and then the combustion gas flows through the secondcombustion gas holes 62 b formed in the second partition plate 60 b andinto the third area R3. In the third area R3, the combustion gas flowsin the direction of the arrow A2, and then the combustion gas flowsthrough the third combustion gas holes 62 c formed in the thirdpartition plate 60 c and into the fourth area R4. In the fourth area R4,the combustion gas flows in the direction of the arrow A1, and then thecombustion gas is discharged to the exterior through the fourthcombustion gas holes 62 d formed in the fourth partition plate 60 d.

The heat exchanger 50 is provided in the second area R2, the reformer 46is provided in the third area R3, and the evaporator 48 is provided inthe fourth area R4. Thus, combustion gas, which is discharged from thefirst area R1, heats the heat exchanger 50, then heats the reformer 46,and then heats the evaporator 48.

After the temperature of the fuel cell module 12 has been raised to apredetermined temperature, the oxygen-containing gas is supplied intothe heat exchanger 50, and the mixed gas of raw fuel and water vapor issupplied into the reformer 46.

More specifically, the opening angle of the oxygen-containing gasregulator valve 112 is adjusted such that the flow rate of air suppliedto the oxygen-containing gas supply pipe 72 is increased. In addition,the opening angle of the raw fuel regulator valve 106 is adjusted suchthat the flow rate of the raw fuel supplied to the raw fuel supplychannel 88 is increased. Further, by operation of the water supplyapparatus 18, water is supplied to the water channel 100.

Thus, as shown in FIGS. 2 and 3, air that has flowed into the heatexchanger 50 is temporarily supplied to the oxygen-containing gas supplychamber 70 a. While air moves inside the heat exchange pipes 64, the airis heated by means of heat exchange with the combustion gas suppliedinto the second area R2. After the heated air has temporarily beensupplied to the oxygen-containing gas discharge chamber 70 b, the air issupplied to the oxygen-containing gas supply passage 42 a of the fuelcell stack 24 through the oxygen-containing gas channel 74 (see FIG. 1).

In the fuel cell stack 24, after the heated air has flowed through theoxygen-containing gas flow field 38, the oxygen-containing gas isdischarged from the oxygen-containing gas discharge passage 42 b andinto the oxygen-containing exhaust gas channel 63 a. Theoxygen-containing exhaust gas channel 63 a opens toward the inside ofthe first partition plate 60 a of the exhaust gas combustor 52, so thatthe oxygen-containing exhaust gas can flow into the first partitionplate 60 a.

Further, as shown in FIG. 1, water from the water supply apparatus 18 issupplied to the evaporator 48. After sulfur has been removed from theraw fuel at the desulfurizer 108, the raw fuel flows through the rawfuel supply channel 88 and moves toward the reformer 46.

In the evaporator 48, after water has temporarily been supplied to thewater supply chamber 98 a, while the water moves inside the evaporationpipes 92, the water is heated by means of the combustion gas that flowsthrough the fourth area R4, and the water is vaporized. After watervapor has flowed into the water vapor discharge chamber 98 b, the watervapor is supplied to the evaporation return pipe 102, which is connectedto the water vapor discharge chamber 98 b. Thus, water vapor flowsinside the evaporation return pipe 102, and further flows into the rawfuel supply channel 88. Then, the water vapor becomes mixed with the rawfuel to produce the mixed gas.

The mixed gas from the raw fuel supply channel 88 is temporarilysupplied to the mixed gas supply chamber 82 a of the reformer 46. Themixed gas moves inside the reforming pipes 76. In the meantime, themixed gas is heated by means of the combustion gas that flows throughthe third area R3. Steam reforming is performed by the catalyst pellets84. After removal (reforming) of C₂₊ hydrocarbons, a reformed gaschiefly containing methane is obtained.

After the reformed gas is heated, the reformed gas is temporarilysupplied as a fuel gas to the reformed gas discharge chamber 82 b.Thereafter, the fuel gas is supplied to the fuel gas supply passage 44 aof the fuel cell stack 24 through the fuel gas channel 90 (see FIG. 1).

In the fuel cell stack 24, after the heated fuel gas has flowed throughthe fuel gas flow field 40, the fuel gas is discharged from the fuel gasdischarge passage 44 b and into the fuel exhaust gas channel 63 b. Thefuel exhaust gas channel 63 b opens toward the inside of the firstpartition plate 60 a of the exhaust gas combustor 52, so that the fuelexhaust gas can be supplied into the first partition plate 60 a.

Under a heating operation of the start-up combustor 54, when thetemperature of the fuel gas in the exhaust gas combustor 52 exceeds theself-ignition temperature, combustion is initiated in the firstpartition plate 60 a between the oxygen-containing exhaust gas and thefuel exhaust gas.

In the first embodiment, the FC peripheral equipment 56 includes thefirst area R1 where the exhaust gas combustor 52 and the start-upcombustor 54 are provided, the annular second area R2 disposed aroundthe first area R1 where the heat exchanger 50 is provided, the annularthird area R3 disposed around the second area R2 where the reformer 46is provided, and the annular fourth area R4 disposed around the thirdarea R3 where the evaporator 48 is provided.

More specifically, the annular second area R2 is disposed in the centeraround the first area R1, the annular third area R3 is disposed aroundthe second area R2, and the annular fourth area R4 is disposed aroundthe third area R3. In such a structure, hot temperature equipment with alarge heat demand such as the heat exchanger 50 (and the reformer 46)can be provided on the inside, whereas low temperature equipment with asmall heat demand such as the evaporator 48 can be provided on theoutside.

For example, the heat exchanger 50 requires a temperature in a range of550° C. to 650° C., and the reformer 46 requires a temperature in arange of 550° C. to 600° C. Further, the evaporator 48 requires atemperature in a range of 150° C. to 200° C.

Thus, an improvement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated. Further, a simple and compactstructure can be achieved. In particular, since the heat exchanger 50 isprovided inside the reformer 46 in an environment where the A/F(air/fuel gas) ratio is relatively low, the reformer 46, which issuitable for carrying out reforming at low temperatures, can be usedadvantageously.

Further, the first partition plate 60 a, the second partition plate 60b, and the third partition plate 60 c separate the first area R1, thesecond area R2, the third area R3, and the fourth area R4, respectively,and the first combustion gas holes 62 a, the second combustion gas holes62 b, and the third combustion gas holes 62 c are formed in the firstpartition plate 60 a, the second partition plate 60 b, and the thirdpartition plate 60 c, respectively, for thereby allowing the combustiongas to flow through the first area R1, the second area R2, the thirdarea R3, and the fourth area R4.

In such a structure, blowing of the combustion gas can be suitablysuppressed, a further improvement in heat efficiency is achieved, and athermally self-sustaining operation can reliably be facilitated.

Further, positions of the first combustion gas holes 62 a, the secondcombustion gas holes 62 b, and the third combustion gas holes 62 c canbe determined depending on a priority of any of heat exchangeefficiency, durability, and reduction in size or the like with respectto the second, third, and fourth areas R2, R3, R4. Accordingly, a targetheat exchange efficiency can be determined freely, and a wider varietyof designs becomes available.

In the first embodiment, the heat exchanger 50 is provided in the secondarea R2, whereas the reformer 46 is provided in the third area R3. Thefirst combustion gas holes 62 a are disposed adjacent to the end of thefirst partition plate 60 a in close proximity to the fuel cell stack 24,and the second combustion gas holes 62 b are disposed adjacent to theend of the second partition plate 60 b opposite from the fuel cell stack24. The third combustion gas holes 62 c are disposed adjacent to the endof the third partition plate 60 c in close proximity to the fuel cellstack 24.

Thus, as shown in FIG. 5, in the second area R2, the flow direction ofthe oxygen-containing gas, which flows through the heat exchanger 50 inthe direction of the arrow A2, is opposite to the flow direction of thecombustion gas, as indicated by the arrow A1, i.e., theoxygen-containing gas and the combustion gas flow in a counterflowingmanner. Owing to such a counterflow structure, as shown in FIG. 6, heatexchange efficiency is good, and the temperature at the heattransmission surface becomes high. Thus, an improvement in heat exchangeefficiency of the heat exchanger 50 can be achieved.

In the third area R3, the flow direction of the mixed gas that flowsthrough the reformer 46 in the direction of the arrow A2, and the flowdirection of the combustion gas, as indicated by the arrow A2, are thesame, i.e., the mixed gas and the combustion gas flow in a parallelmanner. With such a parallel flow structure, as shown in FIG. 7, thetemperature becomes uniform throughout the reformer 46 as a whole, andan improvement in catalyst activity can be achieved. Accordingly, animprovement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated.

In this regard, as shown in FIG. 8, the first combustion gas holes 62 a,which are formed in the first partition plate 60 a, are positioned inconfronting relation to the inner wall surface of the second partitionplate 60 b. In such a structure, the combustion gas can flow reliablyand sufficiently through the second area R2.

Further, in the first embodiment, as shown in FIGS. 2, 3 and 5, thereformer 46 includes the annular mixed gas supply chamber 82 a, theannular reformed gas discharge chamber 82 b, the reforming pipes 76, andthe third combustion gas channel 116 c. Mixed gas is supplied to themixed gas supply chamber 82 a, and the produced fuel gas is dischargedto the reformed gas discharge chamber 82 b. The reforming pipes 76 areconnected at one end thereof to the mixed gas supply chamber 82 a, andare connected at the other end thereof to the reformed gas dischargechamber 82 b. The third combustion gas channel 116 c supplies thecombustion gas into the space between the reforming pipes 76.

The evaporator 48 includes the annular water supply chamber 98 a, theannular water vapor discharge chamber 98 b, the evaporation pipes 92,and the fourth combustion gas channel 116 d. Water is supplied to thewater supply chamber 98 a, and water vapor is discharged to the watervapor discharge chamber 98 b. The evaporation pipes 92 are connected atone end thereof to the water supply chamber 98 a, and are connected atthe other end thereof to the water vapor discharge chamber 98 b. Thefourth combustion gas channel 116 d supplies the combustion gas into thespace between the evaporation pipes 92.

The heat exchanger 50 includes the annular oxygen-containing gas supplychamber 70 a, the annular oxygen-containing gas discharge chamber 70 b,the heat exchange pipes 64, and the second combustion gas channel 116 b.Oxygen-containing gas is supplied to the oxygen-containing gas supplychamber 70 a, and the heated oxygen-containing gas is discharged to theoxygen-containing gas discharge chamber 70 b. The heat exchange pipes 64are connected at one end thereof to the oxygen-containing gas supplychamber 70 a, and are connected at the other end thereof to theoxygen-containing gas discharge chamber 70 b. The second combustion gaschannel 116 b supplies the combustion gas into the space between theheat exchange pipes 64.

As described above, the annular supply chambers (mixed gas supplychamber 82 a, water supply chamber 98 a, and the oxygen-containing gassupply chamber 70 a), the annular discharge chambers (reformed gasdischarge chamber 82 b, water vapor discharge chamber 98 b,oxygen-containing gas discharge chamber 70 b), and the pipes (reformingpipes 76, evaporation pipes 92, and heat exchange pipes 64) are providedas a basic structure. Thus, a simple structure can easily be achieved.Accordingly, the production cost of the entire fuel cell module 12 isreduced effectively. Further, by changing various parameters, such asthe volumes of the supply chambers and the discharge chambers, thelength, the diameter, and the number of pipes, a desired operation canbe achieved depending on various operating conditions, and a widervariety of designs becomes available.

Further, in the first embodiment, the reformed gas discharge chamber 82b, the water vapor discharge chamber 98 b, and the oxygen-containing gasdischarge chamber 70 b are provided on one end side close to the fuelcell stack 24, whereas the mixed gas supply chamber 82 a, the watersupply chamber 98 a, and the oxygen-containing gas supply chamber 70 aare provided on the other end side opposite from the fuel cell stack 24.

In such a structure, reactant gases (fuel gas and oxygen-containinggas), immediately after being raised in temperature and reformingthereof, can be supplied promptly to the fuel cell stack 24. Further,while a decrease in temperature due to radiant heat is minimized,exhaust gas from the fuel cell stack 24 can be supplied to the reformer46, the evaporator 48, the heat exchanger 50, and the exhaust gascombustor 52 of the FC peripheral equipment 56. Accordingly, animprovement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated. The phrase “thermallyself-sustaining operation” herein implies an operation in which theoperating temperature of the fuel cell 22 is maintained using only heatgenerated in the fuel cell 22 itself, without supplying additional heatfrom the exterior.

Further, the combustion gas flows through the first combustion gaschannel 116 a in the first area R1, then through the second combustiongas channel 116 b in the second area R2, then through the thirdcombustion gas channel 116 c in the third area R3, and then through thefourth combustion gas channel 116 d in the fourth area R4. Thereafter,the combustion gas is discharged to the exterior of the fuel cell module12. Thus, it becomes possible to effectively supply heat to the exhaustgas combustor 52, the heat exchanger 50, the reformer 46, and theevaporator 48 of the FC peripheral equipment 56. Accordingly, animprovement in heat efficiency is achieved, and a thermallyself-sustaining operation can be facilitated.

Further, in the evaporator 48, at least one of the evaporation pipes 92forms an evaporation return pipe 102, which connects the water vapordischarge chamber 98 b and the mixed gas supply chamber 82 a of thereformer 46. Thus, in a state in which the water vapor is kept hot, thewater vapor is mixed with the raw fuel in the mixed gas supply chamber82 a of the reformer 46 to thereby obtain the mixed gas. Accordingly, animprovement in reforming efficiency is achieved.

Further, the fuel cell module 12 is a solid oxide fuel cell module.Therefore, the fuel cell module 12 is applicable to high temperaturetype fuel cells such as SOFC.

As shown in FIG. 9, a fuel cell system 130 includes a fuel cell module132 according to a second embodiment of the present invention.Constituent elements of the fuel cell module 132 according to the secondembodiment of the present invention, which are identical to those of thefuel cell module 12 according to the first embodiment, are labeled withthe same reference numerals, and descriptions of such features areomitted.

As shown in FIG. 10, the fuel cell module 132 includes a first area R1comprising, e.g., a circular opening where an exhaust gas combustor 52and a start-up combustor 54 are provided, an annular second area R2disposed around the first area R1 where the reformer 46 is provided, anannular third area R3 disposed around the second area R2 where the heatexchanger 50 is provided, and an annular fourth area R4 disposed aroundthe third area R3 where the evaporator 48 is provided.

The FC peripheral equipment 56 includes a first partition plate 134 aprovided between the first area R1 and the second area R2, a secondpartition plate 134 b provided between the second area R2 and the thirdarea R3, a third partition plate 134 c provided between the third areaR3 and the fourth area R4, and a fourth partition plate 134 d disposedaround the fourth area R4.

As shown in FIGS. 10 and 11, first combustion gas holes 62 a areprovided adjacent to an end of the first partition plate 134 a oppositefrom the fuel cell stack 24, second combustion gas holes 62 b areprovided adjacent to an end of the second partition plate 134 b close tothe fuel cell stack 24, third combustion gas holes 62 c are providednear an end of the third partition plate 134 c opposite from the fuelcell stack 24, and fourth combustion gas holes 62 d are providedadjacent to an end of the fourth partition plate 134 d close to the fuelcell stack 24.

A plurality of gas extraction holes 136 a are formed in the firstpartition plate 134 a opposite from the first combustion gas holes 62 a.Each of the gas extraction holes 136 a has an opening area, which issmaller than each of the opening areas of the first combustion gas holes62 a. As shown in FIGS. 11 and 12, the gas extraction holes 136 a areformed at positions confronting the second combustion gas holes 62 bformed in the second partition plate 134 b. A plurality of gasextraction holes 136 b are formed in the second partition plate 134 b atpositions confronting the third combustion gas holes 62 c formed in thethird partition plate 134 c. A plurality of gas extraction holes 136 care formed in the third partition plate 134 c at positions confrontingthe fourth combustion gas holes 62 d formed in the fourth partitionplate 134 d. The gas extraction holes 136 b, 136 c are not essential,and may be provided only as necessary.

In the second embodiment, the fuel cell module 132 includes the firstarea R1 where the exhaust gas combustor 52 and the start-up combustor 54are provided, the annular second area R2 disposed around the first areaR1 where the reformer 46 is provided, the annular third area R3 disposedaround the second area R2 where the heat exchanger 50 is provided, andthe annular fourth area R4 disposed around the third area R3 where theevaporator 48 is provided.

In this structure, hot temperature equipment with a large heat demandsuch as the reformer 46 (and the heat exchanger 50) are provided on theinside, and low temperature equipment with a small heat demand such asthe evaporator 48 are provided on the outside. Accordingly, animprovement in heat efficiency is achieved, and a thermallyself-sustaining operation is facilitated easily. Further, a simple andcompact structure is achieved.

Moreover, the first partition plate 134 a, the second partition plate134 b, and the third partition plate 134 c separate the first area R1,the second area R2, the third area R3, and the fourth area R4 from eachother. Further, the first combustion gas holes 62 a, the secondcombustion gas holes 62 b, and the third combustion gas holes 62 c areformed in the first partition plate 134 a, the second partition plate134 b, and the third partition plate 134 c, respectively, for therebyallowing the combustion gas to flow through the first area R1, then thesecond area R2, then the third area R3, and then the fourth area R4.

In this regard, as shown in FIG. 11, in the second area R2, the flowdirection of the mixed gas flowing through the reformer 46 in thedirection of the arrow A2, and the flow direction of the combustion gasin the direction of the arrow A2 are the same, i.e., the mixed gas andthe combustion gas flow in a parallel manner. In the third area R3, theflow direction of the oxygen-containing gas that flows through the heatexchanger 50 in the direction of the arrow A2 is opposite to the flowdirection of the combustion gas indicated by the arrow A1, i.e., theoxygen-containing gas and the combustion gas flow in a counterflowingmanner.

Further, the gas extraction holes 136 a are formed in the firstpartition plate 134 a opposite from the first combustion gas holes 62 a.Each of the gas extraction holes 136 a has an opening area, which issmaller than the opening areas of the first combustion gas holes 62 a.In the presence of the gas extraction holes 136 a, a portion of thecombustion gas flows from the first area R1, through the second area R2,and into the third area R3. Thus, the quantity of heat required by theheat exchanger 50 in the third area R3 can be supplemented, whereby itis possible to maintain a thermally self-sustaining operation.

Accordingly, in the second embodiment, a further improvement in heatefficiency is achieved, and a thermally self-sustaining operation isfacilitated reliably. Further, the same advantages as those of the firstembodiment are obtained. For example, the temperature becomes uniformthroughout the reformer 46 as a whole, and an improvement in catalystactivity is achieved. Moreover, an improvement in heat exchangeefficiency of the heat exchanger 50 is achieved. In particular, sincethe reformer 46 is provided inside the heat exchanger 50, in anenvironment where the A/F (air/fuel gas) ratio is relatively high, thereformer 46, which is suitable for reforming at high temperature, can beused advantageously.

Although certain preferred embodiments of the present invention has beenshown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

The invention claimed is:
 1. A fuel cell module comprising: a fuel cellstack formed by stacking fuel cells for generating electricity byelectrochemical reactions between a fuel gas and an oxygen-containinggas; a reformer for reforming a mixed gas of water vapor and a raw fuelchiefly containing hydrocarbon to produce the fuel gas supplied to thefuel cell stack; an evaporator for evaporating water, and supplying thewater vapor to the reformer; a heat exchanger for raising temperature ofthe oxygen-containing gas by heat exchange with combustion gas, andsupplying the oxygen-containing gas to the fuel cell stack; an exhaustgas combustor for combusting the fuel gas discharged from the fuel cellstack as a fuel exhaust gas and the oxygen-containing gas dischargedfrom the fuel cell stack as an oxygen-containing exhaust gas to therebyproduce the combustion gas; and a start-up combustor for combusting theraw fuel and the oxygen-containing gas to thereby produce the combustiongas, the fuel cell module further comprising: a first area where theexhaust gas combustor and the start-up combustor are provided; anannular second area disposed around the first area where one of thereformer and the heat exchanger is provided; an annular third areadisposed around the second area where another of the reformer and theheat exchanger is provided; an annular fourth area disposed around thethird area where the evaporator is provided; a first partition plateprovided between the first area and the second area; a second partitionplate provided between the second area and the third area; and a thirdpartition plate provided between the third area and the fourth area,wherein a plurality of first combustion gas holes, a plurality of secondcombustion gas holes, and a plurality of third combustion gas holes areformed in the first partition plate, the second partition plate, and thethird partition plate, respectively, for thereby allowing the combustiongas to flow through the first area, the second area, the third area, andthe fourth area, the plurality of first combustion gas holes are formedin the first area at a first end of an axial direction, the plurality ofsecond combustion gas holes are formed in the second area at a secondend of the axial direction, the plurality of third combustion gas holesare formed in the third area at the first end of the axial direction, inthe heat exchanger, the oxygen-containing gas and the combustion gasflow in an opposite direction, and in the reformer, the mixed gas andthe combustion gas flow in a same direction.
 2. The fuel cell moduleaccording to claim 1, wherein the reformer includes an annular mixed gassupply chamber to which the mixed gas is supplied, an annular reformedgas discharge chamber to which the produced fuel gas is discharged, anda plurality of reforming pipes connected at one end to the mixed gassupply chamber, and connected at another end to the reformed gasdischarge chamber, and a combustion gas channel for supplying thecombustion gas to a space between the reforming pipes; the evaporatorincludes an annular water supply chamber to which the water is supplied,an annular water vapor discharge chamber to which the water vapor isdischarged, a plurality of evaporation pipes connected at one end to thewater supply chamber, and connected at another end to the water vapordischarge chamber, and a combustion gas channel for supplying thecombustion gas to a space between the evaporation pipes; and the heatexchanger includes an annular oxygen-containing gas supply chamber towhich the oxygen-containing gas is supplied, an annularoxygen-containing gas discharge chamber to which the heatedoxygen-containing gas is discharged, a plurality of heat exchange pipesconnected at one end to the oxygen-containing gas supply chamber, andconnected at another end to the oxygen-containing gas discharge chamber,and a combustion gas channel for supplying the combustion gas to a spacebetween the heat exchange pipes.
 3. The fuel cell module according toclaim 2, wherein the reformed gas discharge chamber, the water vapordischarge chamber, and the oxygen-containing gas discharge chamber areprovided on one end side close to the fuel cell stack; and the mixed gassupply chamber, the water supply chamber, and the oxygen-containing gassupply chamber are provided on another end side opposite from the fuelcell stack.
 4. The fuel cell module according to claim 3, wherein thecombustion gas flows through a combustion gas channel in the first area,then flows from the first combustion gas holes to the combustion gaschannel in the second area, then flows from the second combustion gasholes to the combustion gas channel in the third area, and then flowsfrom the third combustion gas holes to the combustion gas channel in thefourth area, and thereafter, the combustion gas is discharged toexterior of the fuel cell module.
 5. The fuel cell module according toclaim 3, wherein the heat exchanger is provided in the second area, andthe reformer is provided in the third area; the first combustion gasholes are provided adjacent to an end of the first partition platedisposed close to the fuel cell stack; the second combustion gas holesare provided adjacent to an end of the second partition plate oppositefrom the fuel cell stack; and the third combustion gas holes areprovided adjacent to an end of the third partition plate disposed closeto the fuel cell stack.
 6. The fuel cell module according to claim 3,wherein the reformer is provided in the second area, and the heatexchanger is provided in the third area; the first combustion gas holesare provided adjacent to an end of the first partition plate oppositefrom the fuel cell stack; the second combustion gas holes are providedadjacent to an end of the second partition plate disposed close to thefuel cell stack; and the third combustion gas holes are providedadjacent to an end of the third partition plate opposite from the fuelcell stack.
 7. The fuel cell module according to claim 2, wherein atleast one of the evaporation pipes forms an evaporation return pipe,which is connected to the water vapor discharge chamber and the mixedgas supply chamber.
 8. The fuel cell module according to claim 1,wherein the fuel cell module is a solid oxide fuel cell module.